Use of Air with Different Solvents Mixtures for Improved Foam Stability and Cost Effective Heavy Oil Recovery

Abstract

Abstract Foamy oil flow is commonly encountered in heavy oil production from homogeneous or heterogeneous (after cold heavy oil production with sands - CHOPS) reservoirs. This can be due to a drive mechanism in the primary production (depletion of methane saturated heavy-oil) and secondary stage (gas injection after primary production). In the primary stage, among other important parameters, pressure depletion rate has been reported to be the most critical characteristic to control this type of flow. In the secondary stage, gas amount and type (sole injection of methane, carbon dioxide, propane, or combination of these) and application conditions (soaking time on cyclic solvent injection durations, depletion rate) are critical. The cornerstone of the foamy oil behavior relies on its stability, which depends on parameters such as oil viscosity, temperature, dissolved gas ratio, pressure decline rate, and dissolved gas (solvent) composition. Although the process has been investigated and analyzed for different parameters in the literature, the optimal conditions for an effective and more economical process (mainly foamy oil stability) has not been thoroughly understood, especially for the secondary recovery conditions. In this study, air has been used as an ameliorative to improve foamy oil stability. Five pressure depletion tests divided into two cases were performed. Each pressure depletion test included eight independent pressure recordings obtained from pressure transducers distributed along a sandpack holder for 48 hours. In order to reach the optimal conditions of the applications, three different pressure depletion rates were tested at 0.23 psi, 0.51 psi/min, 1.53 psi/min, and air were tested as an ameliorative for foamy oil stability. We observed that increasing pressure depletion rates increase the formation of foamy oil, however, when pressure depletion rates were too high, it may cause a negative effect in the final oil recovery factor. We also observed that injecting air into the sandpack caused an increase in the heavy oil viscosity, and the subsequent injection of methane as a solvent became more effective in generating more stable foamy oil, which resulted in obtaining a higher oil recovery factor. This novel approach is expected to improve the understanding and the use of foamy oil mechanics and to achieve a higher foamy oil stability aiming to increase the final heavy oil recovery factor.